Population changes of Adélie and emperor penguins along the Prince Olav Coast and on the Riiser-Larsen Peninsula

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1 Polar Biosci., +1, ++1 +,,,,**.,**. National Institute of Polar Research Scientific note Population changes of Adélie and emperor penguins along the Prince Olav Coast and on the RiiserLarsen Peninsula Akiko Kato +, Kentaro Watanabe +,, and Yasuhiko Naito +,, + National Institute of Polar Research, Kaga +chome, Itabashiku, Tokyo +12/+/ ( akikato@nipr.ac.jp), The Graduate University for Advanced Studies, Kaga +chome, Itabashiku, Tokyo +12/+/ (Received April +*,,**; Accepted June *,,**) Abstract: The trends of penguin populations are thought to be reliable indicators of ecosystem changes in the Southern Ocean. There are seven Adélie penguin colonies and one emperor penguin colonyalong the Prince Olav Coast and one emperor penguin colonyon the RiiserLarsen Peninsula. We compiled and analyzed the available data collected byairborne and ground census between +31+ and,*** in order to determine the breeding status of penguins in this area. Adélie penguin populations increased at two colonies; no apparent trends were observed at other colonies. Emperor penguin populations were high in the mid+33*s and suddenlydecreased in,***. Populations need to be carefullymonitored in the coming years. key words: Adélie penguin, emperor penguin, population, East Antarctica Introduction The trends of penguin populations are thought to be reliable indicators of environmental changes occurring in the Southern Ocean. Adélie penguins are decreasing in the Antarctic Peninsula area and increasing in East Antarctica and the Ross Sea area (Woelher et al.,,**+; Croxall et al.,,**,). The onlylongterm data set available for emperor penguin, breeding in Adélie Land, shows that the population there was stable from the +3/*s to the mid+31*s, followed bya rapid decline in the late +31*s, and has stabilized since (Barbraud and Weimerskirch,,**+). The increase of air temperature and decrease of sea ice are thought to be the main causes for these population changes (Barbraud and Weimerskirch,,**+; Wilson et al.,,**+; Croxall et al.,,**,). There are seven Adélie penguin colonies and one emperor penguin colonyalong the Prince Olav Coast, EnderbyLand and one emperor penguin colonyon the RiiserLarsen Peninsula (Hoshiai and Chujo, +310; Hoshiai and Matsuda, +313; Hoshiai et al., +32.; Ishikawa et al., +322). These colonies were discovered during the Japanese Antarctic Research Expeditions (JARE) and have been monitored occasionallybyairborne and ground census since We compiled and analyzed the data collected between +31+ and,*** in order to determine the breeding status and population trends of penguins in this area. ++1

2 118 A. Kato, K. Watanabe and Y. Naito Materials and methods Breeding colonies of Adélie penguins along the Prince Olav Coast, Enderby Land were observed occasionally between November and January from +31+ to the present by JARE. Penguins were counted three times from aerial photographs or directly on the ground. Average values were used for the analysis. In the LützowHolm Bay area penguins started to arrive at the colonies around midoctober. Numbers peaked in midnovember before decreasing through late November and finally stabilizing in early December (Watanuki and Naito, +33,). Numbers of breeding pairs (NP) were estimated from the numbers of individuals (NI) for each period using the following equations (Watanuki and Naito, +33,): +* +. November: NP NI/,,,,,2 November: NP.. *.11 NI, / +. December: NP NI. Population trends were tested by regression analysis using StatView (SAS Institute Inc., U.S.A.). There were one emperor penguin colony at Umebosi on the Prince Olav Coast and one on the RiiserLarsen Peninsula. Numbers of individuals were counted between August (chickbrooding) and December (cre che) from aerial and ground photographs. Until September, cre ches had not formed and adults and chicks could be distinguished on photos. In October, the cre ches formed, the number of adults in the colony decreased and it became di$cult to distinguish adults and chicks on photos. Thus, we compared the numbers of adults counted between,, August and,2 September. Results There were seven breeding colonies of Adélie penguins in the icefree areas along the Prince Olav Coast (Fig. +, Table +) that ranged in size between 2* and 0** pairs during +31+,*** (Fig.,, Appendix). At Cape Hinode and Akarui Point, the populations of Adélie penguins increased since the +31* s at annual rates of 1.+ (P *.*+) and,.* (P *.*/), respectively, though no significant trends was observed at other colonies. At Cape Omega and Byôbu, breeding populations tended to increase during the +33* s. Both breeding colonies of emperor penguins on the RiiserLarsen Peninsula and at Umebosi were on the fast seaice at the foot of a cli# of the ice shelf. Population size fluctuated between.*** and 3*** pairs on the RiiserLarsen Peninsula and between,** and 0** pairs at Umebosi during +32.,*** (Table +, Fig., Appendix). Populations of both colonies during the mid+33*s were twice to three times greater than those during the +32*s, but they suddenly decreased to half of the +33*s populations in,***. Discussion Adélie penguins are found around the entire Antarctic continent and their population changes have been monitored in many places. The trends of Adélie penguin

3 Penguin populations in East Dronning Maud Land 119 Fig. +. Map of the study area. Arrows show the breeding colonies of Adélie and emperor penguins (see Table +). Table +. Breeding locations of Adélie and emperor penguins along the Prince OlavCoast and on the RiiserLarsen Peninsula. The numbers correspond to the arrows in Fig. +. Species Location No. Adélie penguin Emperor penguin Cape Omega Akarui Point Tenmondai Byôbu Niban Cape Hinode Cape Ryûgû RiiserLarsen Pen. Umebosi (02..3 S,., *+.. E) (02,1./ S,.+,/./ E) (02,..+ S,.+./., E) (02,,./ S,., *+.3 E) (02 +/.1 S,.,,3.0 E) (02 *2.0 S,., 3.2 E) (01 /2.* S,. /0.. E) (02.2. S,.,.1 E) (02 *,.2 S,. *..3 E),. / Fig.,. Population changes of Adélie penguins at breeding colonies along the Prince OlavCoast.

4 120 A. Kato, K. Watanabe and Y. Naito Fig.. Population changes of emperor penguins on the RiiserLarsen Peninsula and at Umebosi. populations are closely related to seaice characteristics, which can be a#ected by climate changes (Fraser et al., +33,; Smith et al., +333; Wilson et al.,,**+). Although information on climate change and population trends in East Antarctica is limited, Adélie penguin populations have been reported to increase there since the +30*s (Woelher et al.,,**+). The longterm population increases in East Antarctica may also be related to globalscale environmental changes, for example in the Ross Sea area (Taylor et al., +33*; Wilson et al.,,**+). A similar trend has been observed for the populations of the Sôya Coast area in LützowHolm Bay (Kato et al.,,**,). The Sôya Coast is located inside of the bay and sea ice often remains even during the summer, while the Prince Olav Coast, east of LützowHolm Bay, faces the ocean and most of the sea ice present in front of the colonies disappears during the summer. Therefore, environmental conditions in the foraging areas of penguins from these two locations are expected to di#er. Nevertheless, the longterm population trends were similar in these two areas. Over the last.* years, seaice extent has fluctuated substantially, especially in winter, but no significant tendency, toward either an increase or a decrease, was evident between +31+ and,**+ in this area (Kato et al.,,**,). Emperor penguins breed on fast sea ice during the Antarctic winter and their population data are very limited (Barbraud and Weimerskirch,,**+) because of the inaccessibility of the breeding colonies during winter. Although population data in our study colonies were limited, populations increased from the +32* s to the mid+33*s and suddenly decreased in,***. As penguins are longlived seabirds, actual population size does not change much on an annual basis. A sudden decrease might reflect a decrease in the attendance rate at the breeding colony. However, populations will need to be carefully monitored in coming years. Because of the strong link between Antarctic penguin populations and the annual extent of seaice, environmental changes in forthcoming years, especially global warming issues, should be carefully considered. This is especially true in our study area (including the RiiserLarsen Peninsula, LützowHolm Bay and the Prince Olav Coast)

5 Penguin populations in East Dronning Maud Land 121 where seaice condition varies considerably on a limited spatial scale. Moreover, environmental data are continuously available from the JARE monitoring program. Acknowledgments We thank Y. Takahashi, H. Uenishi, and Y. Watanuki for their countless e#orts in counting thousands of penguins and compiling the data set. Special thanks are due to many JARE expeditioners who counted penguins in the study areas during the period +31+,***. Y. RopertCoudert helped to improve the manuscript and Y. Watanuki provided valuable comments on the manuscript. References Aoyanagi, M. (+31): On the activity of Adélie penguin (Pygoscelis adeliae) at Cape Hinode, Prince Olav Coast, Antarctica. Nankyoku Shiryô (Antarct. Rec.),.0, +* +++ (in Japanese with English abstract). Barbraud, C. and Weimerskirch, H. (,**+): Emperor penguins and climate change. Nature,.++, Croxall, J.P., Trathan, P.N. and Murphy, E. J. (,**,): Environmental change and Antarctic seabird populations. Science,,31, +/+* +/+.. Fraser, W.R., Trivelpiece, W.Z., Ainley, D.G. and Trivelpiece, S.G. (+33,): Increases in Antarctic penguin populations: reduced competition with whales or a loss of sea ice due to environmental warming? Polar Biol., ++, /,/ /+. Hoshiai, T. and Chujo, K. (+310): A new emperor penguin rookery of RiiserLarsen Peninsula, East Antarctica. Nankyoku Shiryô (Antarct. Rec.), /1, Hoshiai, T. and Matsuda, T. (+313): Adélie penguin rookeries in the LützowHolm Bay area and relation of rookery to algal biomass in soil. Mem. Natl Inst. Polar Res., Spec. Issue, ++, +.* +/,. Hoshiai, T., Matsuda, T. and Naito, Y. (+32+): Fluctuation of Adélie penguin populations in two small rookeries of Syowa Station area, Antarctica. Nankyoku Shiryô (Antarct. Rec.), 1, Hoshiai, T., Sweda, T. and Tanimura, A. (+32.): Adélie penguin census in , and +32, 2 breeding seasons near Syowa Station, Antarctica. Mem. Natl Inst. Polar Res., Spec. Issue,,, ++1 +,+. Ishikawa, S., Matsuda, O. and Kawaguchi, K. (+322): Adélie penguin census in the / breeding season near Syowa Station, Antarctica with reference to the banding e#ect on the population. Nankyoku Shiryô (Antarct. Rec.),,, *, *1. Kato, A., RopertCoudert, Y. and Naito, Y. (,**,): Changes in Adélie penguin breeding populations in LützowHolm Bay, Antarctica, in relation to seaice conditions. Polar Biol.,,/, Smith, R.C., Ainley, D., Baker, K., Domack, E., Emslie, S., Fraser, B., Kennett, J., Leventer, A., Mosley Thompson, E., Stammerjohn, S. and Vernet, M. (+333): Marine Ecosystem sensitivity to climate change. Historical observations and paleoecological records reveal ecological transition in the Antarctic Peninsula region. BioScience,.3, 3.*.. Taylor, R.H., Wilson, P.R. and Thomas, B.W. (+33*): Status and trends of Adélie penguin populations in the Ross Sea region. Polar Rec.,,0,,3 *.. Watanuki, Y. and Naito, Y. (+33,): Counting Adélie penguins at colonies: seasonal and annual changes. Nankyoku Shiryô (Antarct. Rec.), 0,,13,2. (in Japanese with English abstract). Wilson, P.R., Ainley, D.G., Nur, N., Jacobs, S.S., Barton, K. J., Ballard, G. and Comiso, J.C. (,**+): Adélie penguin population change in the pacific sector of Antarctica: relation to seaice extent and the Antarctic Circumpolar Current. Mar. Ecol. Prog. Ser.,,+, *+ *3. Woehler, E. J., Cooper, J., Croxall, J.P., Fraser, W.R., Kooyman, G.L., Miller, G.D., Nel, D.C., Patterson, D.L., Peter, H.U., Ribic, C.A., Salwicka, K., Trivelpiece, W.Z. and Weimerskirch, H. (,**+): A statistical assessment of the status and trends of Antarctic and subantarctic seabirds. Report on SCAR BBS Workshop on Southern Ocean Seabirds Populations,. p.

6 122 A. Kato, K. Watanabe and Y. Naito Appendix. Date of censuses for Adélie and emperor penguins. Adélie penguin Emperor penguin Year Cape Omega Akarui Point Tenmondai Byôbu Niban Cape Hinode Cape Ryûgû Riiser Larsen Umebosi * ,*** +. Nov.,, Nov., +. Nov., Nov., Nov., Nov.,2 Nov. +, +. Nov.,2 Nov., Nov.,2 Nov.,/ Sep. +. Sep. +1 Sep. + Aug. 3 Sep. +, Sep.,2 Sep.,, Aug. ++ Sep. 3 Sep. + Sep. Ground census References: + Aoyanagi (+31);, Hoshiai and Matsuda (+313); Hoshiai et al. (+32+)